Element.prefix is a read-only property that returns the element’s namespace prefix as a string, or null if none is specified (MDN).
Read the notes below before you get or set this property. Prefer feature detection when support is limited.
Use el.prefix. Start with this line.
element.prefix| Call | What it does |
|---|---|
element.prefix | Primary signature. |
Built into the browser. Read or assign el.prefix — no import required.
element.prefixThis member has no parameters beyond those shown in the signature.
| Return Value | Description |
|---|---|
| * | String or null |
nullNormal HTML tags in an HTML document have no namespace prefix.
const box = document.createElement("div");
console.log(box.prefix); // null
console.log(box.localName); // "div"x: style prefix in the name.prefix. There is none → null.localName still works. You get "div".null for everyday HTML DOM work.createElementNSPass a qualified name with a prefix to set prefix at creation.
const NS = "http://example.com/x";
const el = document.createElementNS(NS, "x:box");
console.log(el.prefix); // "x"
console.log(el.localName); // "box"
console.log(el.namespaceURI); // "http://example.com/x"NS."x:box". The part before : becomes the prefix."box" only), prefix stays null.Use a namespace-aware XML parse so x:div keeps its prefix.
const xml = '<x:div xmlns:x="http://example.com/x"/>';
const doc = new DOMParser().parseFromString(xml, "application/xml");
const el = doc.documentElement;
console.log(el.prefix); // "x"
console.log(el.localName); // "div"xmlns:x.application/xml. That uses a namespace-aware parser.documentElement.prefix. You get "x" (MDN’s idea).localName is "div" — the part after the colon.Element.prefix is Baseline Widely available (MDN: since July 2015). The property exists everywhere; non-null values depend on namespace-aware creation/parsing.
Read-only namespace prefix string or null — useful mainly with XML / createElementNS.
Bottom line: Safe API. For real prefixes, use XML parsing or a prefixed createElementNS name.
Learn how to read the previous sibling Element in the DOM tree.
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